Structure of the photosynthetic apparatus in woody plants from different ecological and altitudinal groups in Eastern Pamir

The structure of photosynthetic apparatus was quantitatively characterized for 15 species of woody plants (low shrubs, semishrubs, and cushion plants) inhabiting Eastern Pamir at elevations between 3800 and 4750 m. Assimilatory organs of the plants investigated featured common adaptive modifications, such as small and thick leaves, a high weight per unit leaf area, extensive development of palisade mesophyll, and an increased number of chlorenchyma cells and chloroplasts per unit leaf area. These leaf features serve to enlarge the internal assimilatory surface and to decrease resistance to CO2 diffusion, which is essential under moisture deficit. Comparative analysis of leaf structure revealed characteristics dividing woody plants of Eastern Pamir into several groups according to their life forms, ecological groups, and types of mesophyll structure. It is suggested that whole plant characteristics (life form), combined with quantitative characteristics of structure, would help to identify the functional types of high mountain plants.